Hartford - A bill that would decriminalize but not legalize the possession of small amounts of marijuana passed the state Senate Saturday afternoon by the thinnest of margins and is headed to the House.

Lt. Gov. Nancy Wyman, a Democrat, broke an 18-18 tie vote. The bill sets a $150 fine for a first offense of possessing a half-ounce or less of marijuana. Second-time offenders would be fined between $200 and $500 and required to enroll in a drug education program at their own expense.

If it passes both chambers, the governor has said he will sign it.

Violators who are under 21 would have their driver's licenses suspended for 60 days.

Under current law, individuals holding less than 4 ounces of marijuana face punishment of up to a year in prison and a $1,000 fine. That penalty would still apply to those caught with more than a half-ounce but less than 4 ounces.

The bill's proponents said prison time is too severe a penalty for minor possession, especially for young people who make a poor decision and then carry a criminal record that could bar them from attending college, landing jobs or serving in the military.

"I think this is better for young people," said Sen. Edith Prague, D-Columbia, who voted for decriminalization. "Going to jail has proven to be a disaster where they come into contact with all kinds of criminals."

Prague added: "This does not legalize marijuana. If kids are caught with marijuana, they lose their licenses, they pay a stiff fine, they just don't go to jail."

Yet other senators argued that the threat of prison is a powerful deterrent for youths who are thinking of trying illicit drugs. They said marijuana has been proven many times to be a gateway drug to substances even more harmful, such as cocaine and heroin.

"The fear of being arrested is a real one," said Republican John Kissel of Enfield. "If you're just going to get a ticket, then all of a sudden the little devil on your shoulder says, 'It's only a ticket.'"

Gov. Dannel P. Malloy initially proposed decriminalizing possession of up to 1 ounce of marijuana. But for Toni Boucher, R-Wilton, the smaller, half-ounce limit in the Senate bill is still too much pot. According to Boucher's research, a half-ounce is enough to roll "30 to 60 joints."

"By relaxing these laws we surely will increase its use," she said.

Several legislators said Saturday that they do not expect a medical marijuana bill to have enough votes to pass this legislation session.

The governor's son, Benjamin Malloy, has had a couple of run-ins with the law that have involved cannabis.

In 2007, when the governor was mayor of Stamford, police accused the young Malloy of dealing marijuana, and he entered a probationary program. Two years later he pleaded guilty to attempted robbery and narcotics charges for a March 2009 incident in which police said he tried to rob a Darien man of marijuana while brandishing a BB gun.

Sens. Andrew Maynard, D-Stonington, and Andrea Stillman, D-Waterford, were also among the 18 lawmakers who voted for decriminalization.

Maynard said the current marijuana possession laws are clogging the courts with small-time, nonviolent offenders.

"I think this is appropriate for the very small amounts," he said.

j.reindl@theday.com